Primary Coolant System Flashcards
From memory, draw and label a one line diagram of the Primary Coolant System showing the following major components and system interfaces:
- Reactor Vessel
- PCS Hot Legs
- Pressurizer
- Pressurizer Safety Valves
- Power Operated Relief Valves
- Quench Tank
- Steam Generators
- PCS Cold Legs
- Primary Coolant Pumps
- Pressurizer Spray Headers
- All Control Room indications
- System Interfaces
Draw use Triangle Notes for Standard
What is the operational design and normal operating range for the PCS Hot Legs?
Hot: 42-inch inside diameter piping
- Interior clad with stainless steel
- 2500 psia, 650°F
- 12-inch inside diameter Surge Line connected to Loop 1 Hot Leg. 2500 psia, 700°F.
- 12-inch inside diameter Shutdown Cooling nozzle (suction) connects to Loop 2 hot leg
What is the operational design and normal operating range for the Pressurizer?
Maintains PCS operating pressure and compensates for changes in the PCS volume during load changes.
- Uses Pressurizer heaters and spray flow for pressure control. CVCS charging and letdown for volume control.
Water volume is sized such that the PZR:
- Does not drain during reactor trip or loss of load transients
- Heaters are not uncovered during 5% and 15% ramps or 10% step load decreases.
- Sizing for limiting DBA - energy released in containment
The steam volume is such that:
- Pressure response during normal load changes does not exceed » ± 50 psi.
- Insurge during a loss of load transient will not reach the safety valve nozzles.
What is the operational design and normal operating range for the Pressurizer Safety Valves?
Sized to limit PCS over-pressure to 110% of design pressure (2500 psia/2750 psia) following a complete loss of generator load without a simultaneous trip of the reactor.
Capacity – 230,000 lb/hr each
RV-1041 – 2500 psia
RV-1040 – 2540 psia
RV-1039 – 2580 psia
What is the operational design and normal operating range for the Power Operated Relief Valves (PORVs)?
PRV‑1042B (125V DC, D11-1), PRV-1043B (125V DC, D21-1):
- Over-pressure protection during periods of low temperature or water solid system operation.
- Aligned for automatic system pressure relief prior to 430°F
- Emergency depressurizaton (loss of offsite power): EOP Space
- Once through cooling in some accident EOP space
Two modes of operation – LTOP and SDC
- LTOP – PORV setpoint and alarm setpoints are variable based on system pressure and cold leg temperature.
- SDC – fixed setpoint for relief and alarm; Pretrip – 265 psia, Trip – 310 psia
What is the operational design and normal operating range for the Quench Tank?
Receives and condenses the normal discharges from the pressurizer safety and relief valves, and prevent the discharge from being released to the containment atmosphere.
Pressure – 100 psig; NOP – 3 psig (N2 cover gas)
Temperature – 340°F; NOT – 104°F
Normal Operating Level – 75%
Water volume (800 ft3) to condense total steam mass released during a 112% to 0% reactor power swing.
Gas volume (347ft3) to limit max tank pressure after the steam release to one half of rupture disc set point of 100 psig (assumes max initial gas pressure of 10 psig).
What is the operational design and normal operating range for the Steam Generators?
U-tube Steam Generators (8,219 tubes)
Feedwater enters the S/Gs through the feed ring, mixes with recirculating water from the moisture separators and flows into the downcomer
J-tubes on the feed ring prevent draining of the feed ring during periods of no feedwater flow. Minimized water hammer during stops and starts of flow.
Steam exiting the steam generator through the steam flow restricting nozzle has a moisture content of less than 0.25% moisture at design flow rate.
Restricting nozzle limits MSLB impacts.
What are the inputs/outputs to the Quench Tank?
Inputs
- Pressurizer safety and relief valves
- Reactor Head Vents
- Pressurizer Vents
- Shutdown Cooling Relief Valve Discharge
- SI Tank Drain Relief Valves
- Letdown Line Relief
Outputs
- Drains to Primary Coolant Drain Tank via CV-0148.
- Vents to the Containment Vent Header via CV-0152.
What is the operational design and normal operating range for the PCS Cold Legs?
30-inch inside diameter piping
- Interior clad with stainless steel.
- no individual supports
- 2500 psia, 650°F
- Thermal sleeves are installed on all 2-inch or greater inlet nozzles to reduce thermal shock effects from auxiliary systems
- 12-inch inside diameter Safety Injection nozzles connect each cold leg and are Angled 30° from vertical towards Rx vessel
What is the gallons per percent and volume of Pressurizer?
- approximately 66 gal/%.
- Volume - 1500 ft3,
- 800 ft3 water at full power
What are the pressurizer block valves?
(MO-1042A, MO‑1043A) provide isolation to PORVs
Controlled by 2-position CLOSE-OPEN switches:
JOG control feature in OPEN direction only – valve only travels when switch is held. Prevents inadvertent opening and allows pilot chamber pressure to slowly equalize
MO-1042A – MCC-25
MO-1043A – MCC-26
When does the Quench Tank rupture disk blow?
100 psig
a 10 psig starting pressure is assumed for time to rupture calculations.
RUD-0162, Rupture Disc, is sized to pass the greatest anticipated discharge, which occurs during a loss of load incident without a reactor trip.
What design features and interlocks provide Primary Coolant System leakage detection?
- Containment sump level indication
- Containment atmosphere gaseous activity monitoring
- Containment air cooler condensate level switches
- Containment atmosphere humidity monitoring
- Monitoring of Quench Tank Level and Pressure as well as the tailpipe temperatures could indicate PCS leakage onto the Quench Tank.
What design features and interlocks provide Primary Coolant System Overpressure protection?
Power Operated Relief Valves (PORVs) PRV‑1042B, PRV-1043B via LTOP
Over-pressure protection during periods of low temperature or water solid system operation via LTOP or SDC mode.
LTOP – PORV setpoint and alarm setpoints are variable based on system pressure and cold leg temperature
Aligned for automatic system pressure relief prior to 430°F
SDC Mode Pretrip – 265 psia.Trip – 310 psia
Given plant conditions, predict downstream temperature from a lifting or leaking PORV without error.
Use Mollier Diagram. Go straight across (constant enthalpy process)
Describe normal operating values for Quench Tank:
- Level
- Pressure
- Temperature
Pressure: 3 psig (N2 cover gas)
Temperature: 104°F
Level: 75%
What are the PCS control room indications for temperature?
Hot Leg RTDs:
- 5 in each hot leg: 4 for indication/control, one spare.
- Duel range output: wide: (50°F to 700°F) narrow: (515°F – 615°F)
- NR (515°F – 615°F): Feeds TMM PY-0102 A/B/C/D with 4 channels
- NR (515°F – 615°F): Feeds Tave/Tref controllers TYT-0100, TYT-0200
- NR (515°F – 615°F): Feeds C-12 Indications, plus alarms
- NR (515°F – 615°F): Feeds PPC
- (WR) (50°F to 700°F): Feeds Subcooled Margin Monitor (SMM)
- (WR) (50°F to 700°F): Feeds PTR-0112/PTR-0122
- (WR) (50°F to 700°F): Feeds C-150
Cold Leg RTDS:
- 3 in each leg - located downstream of PCPs to ensure thorough mixing and uniform temperature indication
- wide: (50°F to 700°F) narrow: (515°F – 615°F)
- Feeds same as Hot Lef RTDs, plus:
- (WR) (50°F to 700°F) to C-33
- (WR) (50°F to 700°F) to LTOP
.
What are the PCS control room indications for Steam Generator pressure?
Eight (8) DP transmitters in each loop measure pressure drop across S/Gs.
- 4 pressure taps in each hot leg just before the S/G.
- 2 pressure taps in each suction leg.
Four (4) DP transmitters connected between the 4 hot leg taps and the 2 suction leg taps, resulting in 4 S/G DPs from hot leg to each suction leg.
- The DP sensed by each of the 16 transmitters is indicated on C-12.
- Transmitter outputs are also sent to four analog summers in the low flow trip logic; FI-0102A/B/C/D
- Summation of these signals represents total core flow - 4 separate flow signals.
- Indicate on Panel C-12 and activate one low flow alarm.
- If 2/4 channels indicate a flow less than set point the reactor is tripped.
- All Flow indications must be within 5% of each other
What protects the Steam Generator from over pressure conditions?
24 Safety Valves protect the shell side
12 per steam header
Three Groups of four valves
- 1000 psia
- 1020 psia
- 1040 psia
What are the Sub-Cooled Margin Monitors?
Part of Post-Accident Monitoring
Psat and Tsat are calculated from highest measured temperature value
2 Thots/loop, 1 Tcold/cold leg
Max temperature input is used
EK-1120 “LOW SUBCOOLING MARGIN” at less than 25 F
Y-30 – SMM-0114
Y-40 – SMM-0124
What are the Tave Tref controllers?
Inputs
NR safety grade Thot & Tcold (515°F-615°F)
Turbine 1st stage pressure
Outputs – Tave
Calculates a Tave signal from Tc and Th which is then sent to:
TR-0100 on C-02
Average Temp Display SS (outputs to)
- TI‑0110 Tave digital indication on C-02
- HIC-0780A – Steam Dump Controller
- LIC-0101A/B – Pressurizer Level Control System
Tave from TYT-0200 is sent to TYT-0100 where the Tave loop1/Tave loop 2 deviation alarm is generated at 5°F.
What indications/controls are on C-33?
- Loop 1A WR T-cold
- Loop 2B WR T-cold
- WR Pressurizer Level, (cold calibrated)
- Two: PZR WR Pressure, PI-0105C/D
What are the C-150 Indications?
PCS Loop 1 WR T-cold
- HS-0102C must be in the AHSP for indication and TI-0115C indication at Panel C-33 will be lost
HS-0102C must be in the AHSP position to have the following indications:
- PCS Loop 1 WR T-hot
- PCS Loop 2 WR T-cold
- PCS Loop 2 WR T-hot
What is the AHSP/CR Switch on C-150.
- 2-position Transfer Switch
- Disables CR indications, enables AHSP indications
- CAUTION – prior to transferring HS-0102C to AHSP position ENSURE Average Temp Display Select on Panel C-02 is in the Loop 2 position
- Atmospheric Steam Dump Valves will get a quick open signal if switch is left in the Loop 1 position and transfer is made. Temperature inputs Tc and Th fail HIGH. (Tave fails high)
